A major part of Ajax is manipulating the DOM—adding, showing, hiding, and removing elements, and so on. Although none of this code is terribly hard to write, it can get repetitious. To simplify this, Prototype adds static methods to the Element class (or in the case of browsers that do not properly support Element, it adds the class) that we can use to manipulate parts of the DOM.
Re: Manipulating DOM
A major part of Ajax is manipulating the DOM—adding, showing, hiding, and removing elements, and so on. Although none of this code is terribly hard to write, it can get repetitious. To simplify this, Prototype adds static methods to the Element class (or in the case of browsers that do not properly support Element, it adds the class) that we can use to manipulate parts of the DOM.